Modern electronic systems and particularly those implemented in monolithic integrated circuit form require circuits for converting an unbalanced or single-ended signal which is asymmetrical with respect to a common reference point, into a balanced or differential signal which is symmetrical with respect to the common reference point. The common reference point can be a ground potential, for instance. More particularly, in some applications, such circuits are sometimes required to provide two output currents one of which has a magnitude that varies as the magnitude of the input current and the other of which has a magnitude that varies by the same amount as the magnitude of the input current, but in the opposite direction. For example, if the magnitude of the input current increases by a predetermined amount the magnitude of the first output current is also desired to increase by the predetermined amount and the magnitude of the second output current is desired to decrease by the same predetermined amount. Hence, the magnitudes of the differential output currents are desired to be linear functions of the magnitude of the single-ended input current.
In the prior art, a differential amplifier having one input terminal grounded is sometimes utilized for converting an unbalanced input signal, which is applied to the other input terminal, into a balanced signal. The balanced output signal occurs between the output terminals of the differential amplifier. Generally, the magnitude of the balanced output voltages of such differential amplifiers have logarithmic relations to the magnitudes of the input voltages. Thus, the prior art configuration provides a differential output voltage which has a magnitude that is a nonlinear function of the magnitude of the input voltage. More specifically, if the magnitude of the input voltage is increased by a predetermined amount, the prior art differential amplifier provides differential output voltages having magnitudes which do not change by the predetermined amount. Consequently such prior art amplifiers are not suitable for some of the aforementioned applications requiring differential, linear currents, for instance.